Seven-time victor Roger Federer lost in straight sets to 21-year-old Russian qualifier Andrey Rublev in the third round of the Cincinnati Masters.

The 21-year-old Rublev, who broke the third seed in his first two service games, shed tears of joy after pulling off the biggest win of his career in 62 minutes.

The Swiss 20-time grand slam champion praised Rublev, who converted three of four break points in his win.

World No 3 Federer said: 'He was super clean - defence, offence, serving well. I like the Northern American conditions, the hard courts, fast courts, but Rublev didn't give grant any rhythm. He was everywhere. So it was tough for me, but excellent match by him.

But oh, this last one.

Barty reached the semifinals of the tournament for the first time and moved closer to regaining the No. 1 world ranking Friday by beating Maria Sakkari 5-7, 6-2, 6-0.

The men's bracket has become a qualifier's dream.

The 77th-ranked Nishioka, who shocked compatriot Kei Nishikori on Wednesday, will next face either France's Adrian Mannarino or Belgian 16th seed David Goffin for a place in the semi-finals.

The day began with the ATP fining Nick Kyrgios $113,000 for expletive-filled outbursts that included smashing rackets, insulting a chair umpire and refusing to get ready to return serve during a second-round match the previous night.

Women's top seed Ashleigh Barty held off Anett Kontaveit as the Estonian served for victory before the top seed scraped a 4-6, 7-5, 7-5 triumph into the WTA event quarter-finals.

"The best thing is when my back was against the wall, the tennis was there", Barty said.

Barty, the French Open champion and now ranked No. 2, can move up to the top spot by reaching the final.

"It was a little bit scrappy at times today but proud of the way we were able to fight and hang in there right until the end", said the reigning Roland Garros champion.

Venus Williams won three matches in a row for the first time since March as she defeated Donna Vekic 2-6, 6-3, 6-3.

After a first-round loss in Toronto last week, her ranking slipped to No. 65, her lowest in seven years.

"Yeah I watched it", Federer said, before refusing to comment further. "I didn't think I was feeling the ball badly, but sometimes can't rely on that serve to the one-two punch". "It's fairly simple, keep it simple, but I've got to work hard".